1. Field of the Invention
The present invention relates generally to a composite optical waveguide fiber, and particularly to the fusion splicing of cylindrical glass bodies having different coefficients of thermal expansion.
2. Technical Background
The technological advancement of optical communication systems has resulted in the development of specialty optical waveguide fibers that may provide a number of signal conditioning mechanisms such as, for example amplification of the optical signal, dispersion compensation and gain flattening. In order to be incorporated into optical communication systems, these specialty fibers must be coupled to fiber pigtails or directly to optical waveguide transmission fibers. These specialty fibers often have chemical compositions that result in thermal expansion characteristics that are quite different from the thermal expansion characteristics of the transmission fibers, such as for example silica optical waveguide fibers (for example SMF-28(trademark) single mode optical waveguide fiber, available from Corning Incorporated of Corning, N. Y., USA) and the optical waveguide fibers used as pigtail fibers.
Often, the deployment of these specialty fibers in optical communication systems requires the coupling of the specialty fibers to transmission fibers. The coupling of optical waveguide fibers to one another is advantageously accomplished by fusion splicing the ends of the fibers together using an electric arc fusion splicer. Conventional wisdom holds that the most efficient fusion splicing occurs when the fibers have the same outer diameter. The difference in thermal expansion characteristics between the specialty fibers and transmission fibers result in weak splices due to high residual stresses when the two fibers have the same diameter, thus there is a need for a low residual stress splice between high thermal expansion specialty fibers and low thermal expansion transmission fibers.
One aspect of the invention is an optical fiber device which includes a first cylindrical glass body with a first coefficient of thermal expansion, a first diameter, and a first end. The optical fiber device also includes an optical waveguide fiber. The optical waveguide fiber has a second coefficient of thermal expansion, a second diameter, and a second end fusion spliced to the first end. The first diameter is greater than the second diameter, and the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion. The cylindrical glass body is substantially coaxial with at least a longitudinally extending end portion of the optical waveguide fiber.
In another embodiment, the present invention includes a composite optical waveguide fiber. The composite optical waveguide fiber includes a first optical waveguide fiber with a first diameter and a first outermost layer having a first coefficient of thermal expansion. The composite optical waveguide fiber further includes a second optical waveguide fiber coupled to the first optical waveguide fiber. The second optical waveguide fiber has a second diameter and a second outermost layer, the second outermost layer having a second coefficient of thermal expansion. The first coefficient of thermal expansion is greater than the second coefficient of thermal expansion and the first diameter is greater than the second diameter.
In another embodiment, the present invention includes a reduced stress optical waveguide fiber splice. The reduced stress optical waveguide fiber splice includes a first optical waveguide fiber having a first outer layer, a first diameter, a first light guiding core region and a first end. The first outer layer has a first coefficient of thermal expansion. The reduced stress optical waveguide fiber splice further includes a second optical waveguide fiber having a second outer layer, a second diameter, a second light guiding core region and a second end fusion spliced to the first end. The second outer layer has a coefficient of thermal expansion. The first diameter is greater than the second diameter, and the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion. The first light guiding core region and the second light guiding core region are substantially aligned with one another.
One advantage of the present invention is that it has reduced residual stresses resulting from the mismatch in coefficient of thermal expansion of the fusion spliced optical waveguide fibers.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operations of the invention.